The present invention relates to a backlighting apparatus for visual displays, particularly for flat panel monitors, such as utilized in notebook computers.
A typical flat panel monitor utilizes an LCD as a means of displaying information. LCDs, which allow the display of alphanumeric, graphic or other information, may comprise a medium whose transmittance changes in response to the application of an electrical potential across the medium. The LCDs may be viewed even in an otherwise dark environment by applying illumination uniformly to their rear face. An exemplary backlighting apparatus for an LCD is disclosed in U.S. Pat. No. 4,043,636.
It is desirable for a backlight for LCDs, such as those found in notebook computers, to have certain attributes. Notebook computers are often used during travel and in areas with little light, such as trains and airplanes. Hence, it is desirable that LCDs have an acceptable level of brightness so that the user can easily read the information on the display.
Furthermore, software applications that are used on notebook computers often display color images. Hence, it is preferable that the display have a spectral content that is compatible with the colors displayed on the LCD. It is also desirable that the light source for the monitor be compact so that it will not significantly increase the size and weight of the computer, as notebook computers are frequently used during travel and must often be carried by a user.
Lastly and importantly, the lighting system should provide uniform illumination across the entire area of the display. In particular, the light emerging from the light source should be substantially featureless and free of distortions such as holes or rings. In practice, the requirement of uniform illumination is difficult to achieve, and prior art devices frequently fail to provide a sufficiently uniform source of illumination for LCD displays.
There is thus a need for a simple, compact, lightweight device for backlighting a display panel, particularly an LCD display panel, which provides highly uniform, high-intensity illumination of the entire display panel.